Numbers of Giardia in the Feces of Infected Children *

Abstract

Estimates were made of the number of Giardia in 1,090 stools from 15 infected children over periods of 1 to 3 months. Three patterns of excretion were observed: 1) high, with the parasite abundant in nearly all stools; 2) low, with the parasite detectable in only 40% of the stools and scanty when present; and 3) mixed, with periods of 1 to 3 weeks of high excretion alternating with generally shorter periods of low excretion, and an overall average of about 60% of stools positive. The presence and relative numbers of Giardia in the feces apparently were unrelated to either the consistency of the stools or frequency of defecation. Attempts to increase parasite excretion with purgatives were, on the whole, unsuccessful.

Cyst morphology and sequence analysis of the small subunit rDNA and ef1α identifies a novel Giardia genotype in a quenda (Isoodon obesulus) from Western Australia

“…The shedding of Giardia cysts is typically intermittent and repeat sampling of individuals is generally required to obtain an accurate assessment of prevalence ( Meloni et al, 1993 andO'Handley et al, 1999). For this study, it was not possible to obtain repeat samples from individual animals and it has been estimated that 15-50% of Giardia infections can go undetected if only one stool sample is examined for the presence of cysts ( Danciger andLopez, 1975 andGoka et al, 1990). The detection of…”

Use of an Enzyme Immunoassay Does Not Eliminate the Need To Analyze Multiple Stool Specimens for Sensitive Detection of Giardia lamblia

“…Until relatively recently, definitive diagnosis of this infection was dependent upon microscopic examination of stool specimens for the characteristic cyst and trophozoite forms of Giardia lamblia. Unfortunately, the sensitivity of conventional ovum-and-parasite (O&P) examination on a single stool specimen for G. lamblia has been shown in several studies to be less than optimal (1,4,9,11) and in a recent study conducted in our laboratory was determined to be only 74% (3). The poor sensitivity of a single O&P examination for diagnosing giardiasis is primarily due to intermittent or low-level shedding of parasites by infected individuals (4) and is one of the principal reasons that parasitology textbooks and laboratory manuals recommend that multiple, independently collected stool specimens be obtained for O&P examination (6,7).…”

Evaluation of Three Commercial Assays for Detection of Giardia and Cryptosporidium Organisms in Fecal Specimens

“…Definitive diagnosis requires the microscopic identification of G. intestinalis cysts or trophozoites or C. parvum oocysts in stool samples (11,19). Giardiasis is often hard to diagnose because of intermittent shedding of organisms (6), requiring examination of stool specimens collected over several days. C. parvum may be challenging to detect on modified Kinyoun's acid-fast stained smears due to its small size (4 to 6 m) (20) and variable staining of the oocysts.…”